In the production of subsea wells, such as oil and gas wells, it is a common practice to use a subsea wellhead assembly. When using such an assembly subsea oil well servicing and completion operations are often performed with TFL tools. TFL operations are preferred because the amount of support facilities necessary to conduct the operation is minimal. That is, an immediately adjacent platform or support structure is not necessary. However, TFL operations do require a particular configuration of seafloor equipment. The subsea wellhead must be designed to guide any TFL tool smoothly through the flowline or tubing into the well's tubing string. Furthermore, TFL operations usually require flowline communication between a surface location, such as an operating station, and the subsea wellhead assembly. Frequently, this connection is made with a dual completion flowline which provides a circulation path between the operating station and the well. Typical TFL operations using TFL tools include paraffin scraping, bottomhole pressure and temperature measurements, workover operations, and replacement of standing valves and sub-surface safety valves.
Notwithstanding the added advantages of TFL operations, the additional expense associated with the initial investment to provide TFL capability is high. This added expense is due primarily to increased costs for the dual flowline, the dual completion hardware, and operational costs related to drilling and completing the well for TFL operation. Additionally, a TFL wellhead is a relatively complex piece of equipment and generally requires special fabrication considerations.
Accordingly, the need exists for an improved method and apparatus which would permit the use of TFL tools and the performance of TFL operations without the added expense and hardware associated with providing dual completion lines and associated equipment.